lp Improve Balance and Postoral Control

M.Y. Lee', M.K. Wong2, and F.T. Tang2 'Chang Gung Memorial Hospital, Taipei, Taiwan, Department of Mechanical Engineering 'Chang Gung Memorial Hospital, Taipei, Taiwan, Deportment of Rehabilitation Medicine

ostural instability is defined as less than optimum control of the center of gravity of the body, or of a body part such as the ad or trunk, over a stable or moving base of support [I].

Evaluation under static conditions is referred to as standing steadiness. Postural instability may OCCUr in the CaSe Of patients with neurological damage of the central m " S system (CNS) due to a cerebrovascular accident (CVA) or acquired sec- ondary to trauma. For these patients, standing-balanc training is a crucial therapeutic procedure before walking and self-care training can begin. However, the effectiveness of a standing- balance therapeutic program depends not only on the skills of medical profes- sionals, but also on the adoption of an adequate training device and program.

The use of biofeedback as an ad- junct to physical therapy for people with postural instability can be traced back to the early 1970s, with application in treatment of head and trunk CO

children with developmental disab cept for one study in 1978 [2], biofeedback was not used for treatment of impaired weight shift affecting standing and locomotion until the late 1980s. This latter applica- tion of biofeedback has primarily involved adults with peripheral vestibular deficits and with hemiplegia secondary to a CVA. In the case of postural instability, the biofeedback signal reflects static body alignment and static weight borne by the feet not

this device were: (1) to reinforce purposeful movement for CNS-impaired patients, voluntary rather than passive movement is necessary; (2) purposeful movement requires planning, execu- tion, and comparison between actual and intended movement; (3) sensory biofeedback should be continuous during the move- ment execution; (4) knowledge of discrepancies between actual

intended movements should be presented immediately through some kind of biofeedback; and (5) success-

ful movement should be repeated immediately to aid the patient in retaining proper per-

formance.

Materials and Methods

Biofeedback Training Device The functional design of this new

training device is shown in Fig. 1. Ba- sically, it consists of foot-pressure sens-

ing instrumentation for weight-bearing measurement, a postural correction mirror

for upper extremity postural training, real-time visual weight-bearing biofeedback, hand-suspen-

sion and hip-fixation systems, a hydraulic height-adjustable worktable, and interchangeable hand-exercise boards. In addi- tion, an auditory system gives the patient training instructions and provides alarm

Figure shows the configuration of the device with its simple mechanical and electronic construction designed to keep costs

for the therapist.

detected by conventional methods. The biofeedback therapeutic down. ~h~ concept ofbiofeedback with the standing subjects was strategy is highly effective for patients, as they can immediately use the augmented sensory information to modify motor behav- ior so as to improve postural stability.

Conventional static standing-steadiness training iS mostly done through instructions by a therapist and use of a simple standing table. The conventional standing table is simple in design and lacks a balance monitoring capability. Training is thus very time consuming and labor intensive, and it is inefficient due to a lack of patient participation with quantitative assessment. In this article, we describe a static standing-balance, weight-bearing training device that incorporates biofeedback from a postural correction mirror. The hypotheses for the clinical assessment of

to monitor the distribution of body weight on a dual-force plat- form. F O ~ standing-balance biofeedback, two numerical light emitting diodes (LEDs) and a light-illuminating balance scale were mounted on the center portion of the postural correction mirror. Numerical weight bearing for both feet was shown digi- tally in the right and left LED displays, respectively. The light- illuminating balance scale was used to represent graphically the degree of balance. The red line in the center ofthe scale indicates the balance target (equal weight distribution between two feet). With unequal weight distribution, the green bars grow horizon- tally, to either side of the scale, in proportion to the difference of weight bearing between the two feet. During standing training,

112 IEEE ENGINEERING IN MEDICINE AND BIOLOGY 0739.51 75/96/$5.00@1996 NovembedOetember 1996

Standing Postural Control Training Device

Group

Age (Y/O)

Sex M

1. Functional design of the biofeedback standing balance training device.

Experimental Control Total (n=30) (n=30) (n=60)

45.43k16.92 52.a+i 2.36 49.12+15.15 -

20 22 42 I

I Table 1. Summary of subject data I

weight bome in affected side body weight

- 0.5 x 100% r- I 10 I a I 18 I

Brunnstrom’s Stage

1 Etioloav I

Experimental Control Total

1 CVA I 22 I 28 I 50 I 1 Head injuw I a I 2 I 10 I

II I 7 I 10 I 17 I 111 I 4 I a I 12 I IV

V ~

7

12

Total I 30 I 30 I 60 I

a dynamic update on how close the patient is to achieving standing balance is then provided. The goal of feedback in this application is for the patient to self-com- pensate and hopefully recalibrate his own balance system by combining impaired endogenous proprioceptive information with accurate exogenous visual informa- tion of his weight-bearing status.

In addition to the weight-bearing dis- play, the postural correction mirror was engraved with a series of rectangular grid

lines, which provided visual biofeedback of upper body postural alignment, as shown in Fig. 2. This mirror was mounted on the back side of the standing table, facing the subject. With this design con- figuration, the weight-bearing display was directly in the patient’s line of sight.

The electronics for signal transmission were packaged in an aluminum enclosure mounted on the bottom of the table. A hydraulic table height and titling angle adjustment system was included. In addi-

With this definition, a higher SSI indicates a poorer postural control.

To compare the experimental results, the reduction of average SSI over the en- tire standing training period for both groups was analyzed using a paired t-test. A detailed comparison was also done separately according to the diagnosed Brunnstrom’s stage.

Results In this study, 20 subjects achieved

good standing balance at the end of the second week and were discharged. An- other 15 subjects received standing train- ing for three weeks, and only 25 subjects completed the standing training for four weeks. Table 3 shows the SSI before and after training for three weeks in both groups. The percentage of patients with SSI <IO% increased from 43% (13/30) to 79% (15/19) for the experimental group. For the control group, the change was from 26% (8/30) to 62% (13/21). Table 4 summarizes the balance-training effects in terms of SSI for both groups. At the start

November/Detember 1996 IEEE ENGINEERING IN MEDICINE AND BIOLOGY 113

of training, the average SSIs in the experi- mental and control groups were 15.6% and 16.8%, respectively (p=0.666), indi- cating no statistical difference. However, the SSIs in the experimental and control groups were reduced to 3.5 *2.2% and 10.1 +.6.4%, respectively, after four weeks of training (g~0.02). The average SSIs after one day of training were 9.6% and 15.4% for the experimental and control groups, respectively (p<0.05). These re- sults indicate that there was an immediate training effect using the biofeedback standing-steadiness training.

Tables 5 to 8 show the effects of balance training in both groups for different Brunnstrom’s stages (i.e., 11, IU, IV, and V) of the patients. From these results, it is clear that hemiplegic subjects with a moderate degree of standing-balance impairment (i.e., Brunnstrom’s stage 111) gained significant training benefits with the biofeedback pro- tocol. The lack of statistical significance in the other stages is likely due to the small numbers of patients used in the compari- sons. Figure 3 shows the SSI of both groups in the different training weeks. It is obvious that the SSI dropped significantly in the experimental group compared to the control group. To verify the reliability of our home- made instrumented force plates, repeated measurements of tested subjects were taken to determine the variability that could be expected from the system without a change in static load on the transducers. As we expected, minimal variation was found.

Discussion Balance and postural control are es-

sential to human locomotion. The as- sessment of balance is an integral part of the physical evaluation for a wide vari- ety of patients in rehabilitation, particu- larly for patients following a CVA. Although several studies have reported impairment of balance following a CVA, relatively few studies have been done to document changes in balance with different training protocols. In this study, using either biofeedback or tradi- tional training protocols, the effects of standing-balance training for patients diagnosed with CVA and head injury were compared. It has been suggested that visual feedback information may be useful to help stabilize human posture. The results of our study show that visual and auditory weight-bearing biofeed- back signals incorporated into a stand- ing-balance training device result in an immediate training benefit for most of

0 - 10%

10 - 20%

Table 3. Percentage of patients with different SSI level before and after balance training

for 3 weeks in experimental and control groups

Before After Before After Before After

13 15 8 13 21 28

10 4 14 7 24 11

1 Grouo I Exoerimental Grouo 1 Control Grouo I Total I

30 - 50%

Total

3 0 3 0 6 0

30 19* 30 21 * 60 40*

Pre-training

I Table 4. Progress in SSI over 4 weeks of balance-training duration in experimental and control groups

30 A 15.6f10.5 30 * 16.8f10.3 0.666

Experimental Group Control Group

Day 1

week 1

week 2

1 I I I I

30 A 9.6 -1-9.4 30 * 15.4 -1- 9.55 0.020*

30 7.9 2 5.9 30 12.7 f 7.6 0.010*

30 5.7 f 4.9 30 10.2 f 5.9 0.002*

Experimental Group Control Group

+ I 1 I I I I

I I I I

1 week3 1 19 1 5.3 24 .7 1 21 I 9.2 25 .7 I 0.024* 1

I

1 week4 1 - 1 4 I 3 . 5 e 2 . 2 1 11 I 10.126.41 0.002* 1

week 1

week 2

* P<0.05, A P= 0.020, * P= 0.590.

7 12.7 6.9 10 14.9 2 10.0 0.627

7 11.Of6.3 10 10.6 f 5.1 0.900

I Table 5. Progress in SSI over 4 weeks of balance-training duration for Brunnstrom’s stage I 1 patients I

I - - . I

I 1 No. 1 Mean+SD(%)I No. 1 Mean+.SD(%) 1 P 1 1 Br. Staqe II I I 1 Pre-traininq I 7 1 25.0 k13.7 1 10 1 23.1213.5 1 0.781 1 1 Post-trainina I

I week3 1 6 1 9 . 0 k 4 . 8 I 8 I 8.7-1-5.9 1 0.920 1 1 week4 1 5 1 3.921.9 1 3 I 13.8e11.4 1 0.094 1 patients. This study also reveals that the cumulative training effect ofbiofeedback was significant forpatients with amoder- ate degree of standing-balance impair- ment (i.e., Brunnstrom’s stage I11 patients). Further studies on implement- ingdifferent trainingprotocolsormodify- ing biofeedback signals to evaluate clinical benefits for patients in different Brunnstrom’s stages are suggested

It has also been suggested that center of pressure (COP) paths may be useful for evaluating postural control and gait abnor- malities, since there are different patterns for normal and pathological subjects [3, 41. Kirby [5] studied the influence of foot posi- tion on standing-balance ability by measur- ing the travel and center of pressure displacement in 10 normal subjects. The results indicated that the variations in foot

1 I 4 IEEE ENGINEERING I N MEDICINE AND BIDLOGY November/December 1996

Posture Correction Mirror with Grid Line

Hand Exercise Board

Interchangeable Hand ; Exercise Board

Adjustable Worktable

with Pressure Sensors

Figure 2. Configuration of the new biofeedback static standing training device.

r I -1- Experimental

-Control

-1- Experimental

10.2 12

10

8 \7.9 0.2 --

6 '-1

-- 4 -- 4 6l 5.3

\-

0.2

10.1

Pre-train Day 1 Week 1 Week2 Week3 Week 4

Training of Week

Figure 3. Progress in standing steadiness index over four weeks of balance training duration in experimental and control groups.

position would sigrdicantly affect standing Conclusions balance. Therefore, Codation between foot position and static steadiness index for CVA andhead-injuredpatientswouldbeinteresting.

Imbalance and falls are the leading causes of injury in older adults, and the leading causes of accidental death in

those over age 85 [7,8]. Furthermore, the increase of age-related diseases such as neuro-muscular dysfunction rely heavily on rehabilitation therapy. The effective- ness of the therapy depends of the skill of therapist and the functions of the thera- peutic devices used. The results of this study demonstrated that the newly de- signed standing-training device with weight-bearing biofeedback offers better training for hemiplegia patients than does conventionaltrainingdevices.Theadvan- tages of this new training device are as follows: (1) simple hardware configura- tion with low construction cost makes its use practical both in the hospital setting and in a home-care environment; ( 2 ) vis- ualandauditory feedbackofweight-bear- ing information gives the patient the means for self-postural compensation, withcorrespondingly lessinterventionby a therapist; (3) integrating balance train- ingwithreal-timequantitativeandgraphi- cal illuminating signals makes training more enjoyable for the patient; (4) bio- feedbackcomponentsforlowerandupper extremities (i.e., weight-bearing measur- ing platform and posture correction mir- ror)canbedecoupledandusedindifferent trainingprograms.

Acknowledgment This research was supported by National

Science Council (Taiwan) under Grant No. NSC-85-233 l-B-182-093-MO8.

Ming-Yih Lee received his Ph.D. degree in Me- chanical Engineering from the University of Minnesota, U S A . He is currently an Associate Professor at the Depart- ment of Mechanical En- gineering, Chang Gung

College of Medicine and Technology, and Executive Secretary of the Preparatory Office of Chang Gung University. He is also the Technical Director of the Biomechanics Laboratory and Rehabilita- tion Science and Engineering Service Center at Chang Gung Memorial Hospi- tal, From 1984 to 1992, he worked as a robotic R&D project manager at CIM- CORP Inc. (MN, U.S.A.) before he joined Chang Gung. His current research is fo- cused on rehabilitation engineering, hos- pital automation, and biorobotics. Dr. Lee is a member of IEEE and currently the Co-chairman of the Taiwan Chapter of the IEEE Robotics and Automation Soci- ety. Dr. Lee has published over 50 papers

November/Detember 1996 IEEE ENGINEERING IN MEDICINE AND BIOLOGY 115

* P<0.05. ~

Experimental Group Control Group

Post-training

week 1 6.1 25.7 8.4 c 6.7 0.480

week 2 4.2 f 3.1 9.3 ? 8.9 0.089

week 3 4.3 f 4.5 9.6 ? 8.4 0.242

week 4 4 3.5 t 2.5 0

Br Stage IV

Pre-training

in the areas of robot contouring control, kinematidkinetic performance, and re- habilitation engineering. Two of his pa- pers won the Best Paper awards. Dr. Lee has six patents in the past three years for his newly developed hospital automat- ion systems.

No MeankSD(%) No Mean+SD(%) P

7 1 4 4 + 9 4 7 109r t .60 0 414

May-Kuen Wong was born in Canton, China, in 1950. She graduated from the Department of Medicine of National Tai- wan University in June 1976, and received complete residentship of Physical Medi-

week 1

week 2

week 3

week 4

116

7 7 0 k 5 1 7 1 1 6 k 4 4 0 096

7 4 6 k 3 3 7 9 2 + 6 5 0 120

4 3 8 k 4 2 6 8 4 5 k 5 6 0 200

3 3 2 k 3 1 5 8 3 2 k 4 3 0 125

I I I

cine and Rehabilitation (PM&R) in Na- tional Taiwan University Hospital for four years. She also visited the Rehabilitation Institute of Chicago (RIC) of Northwest- ern University and the Biomechanics Laboratory of the Mayo Clinic in the U S . as a clinical fellow in the past years. She was the Chairman of the Department of Rehabilitation in Chang Gung Memorial Hospital for four years, full-time Associ- ate Professor and the Chairman of Depart- ment of Physical Therapy of Chang Gung College of Medicine and Technology, and she is a part-time Associate Professor of

Br StageV

Pre-training

IEEE ENGINEERING IN MEDICINE AND BIOLOGY

Experimental Group Control Group

No. MeanfSD(%) No Mean+SD(%) P

12 1 1 . 2 f 7 6 5 1 3 6 f 5 6 0 ,529

National Taiwan Uni- versity since 1984. She is also the vice-superin- tendent of Chang Gung Memorial Hospital and chaired the preparatory office of rehabilitation hospital (1500 beds). Dr. Wong has authored

60 published papers and published two books. Her research interests are rehabili- tation medicine, biomechanics, and acu- puncture.

Fuk-Tan Tang was bom in Hong Kong in 1957. He graduated from the Department of Medicine of National Taiwan Uni- versity in 1984, and then received complete resi- dentship in Chang Gung Memorial Hospital,

Taipei. He is currently the Chairman of the Department of Rehabilitation Medicine of Chang Gung Memorial Hospital. He is also a full-time Associate Professor at Chang Gung College of Medicine and Technology. His areas of expertise include rehabilitation medicine, motor control, spinal cord injury, and orthosis (including insole design through foot pressure study).

Address for Correspondence: Dr. Ming Yih Lee, Department of Mechanical En- gineering, Chang Gung College of Medi- cine and Technology, 259 Wen Hwa 1st Road, Taoyuan, Taiwan 33333, R.O.C.

L

References 1. Moore S and Woollacott MH: “The Use of Feedback Devices to Improve Postural Stability.” Physical Therapy Pvactice 2,2: 1-19, 1993. 2. Wannstedt GT and Herman RM: “Use of Augmented Sensory Feedback to Achieve Sym- metrical Standing.” Physical Therapy 58: 553- 559, 1978. 3. Prieto TE, Myklebust JB, and Myklebust BM: “Characterization and Modeling of Postural Steadiness in the Elderly: A Review.” IEEE Transactions on Rehabilitation Engineering 1, 1: 26-32, 1993. 4. Goldie PA, Bach TM, Evans OM: “Force Platform Measures for Evaluating Postural Con- trol: Reliability and Validity.” Arch Phys Meed Rehabil70: 510-516, 1989. 5. Kirby R L “Influence of Foot Position on Stand- ing Balance.” JBiomechunics 40,2: 423-427,1987. 6. Brunnstrom S: “Movement Therapy in Hemi- plegia.” Harper & Row, New York, 1970. 7. Coogler CE: ‘‘Falls and Inbalance.” Rehab Management (April/May) 53, 1992. 8. Tinetti ME and Speechley M: “Prevention of Falls Among the Elderly.” The New England Journal of Medicine 320,16: 1055-1059, 1989.

November/December 1996